Micropump head



Jan. 24, 1967- A. FERRARI ETAL 3,299,827

MICROPUMP HEAD Filed April 26, 1965 ,n 3 l/z ATTORNEY United States Patent 3,299,827 MICROPUMP HEAD Alsides Ferrari, Alberto Guerra, and Marco Taramasso, Milan, Italy, assignors to Snam S.p.A., Milan, Italy, a company of Italy Filed Apr. 26, 1965, Ser. No. 451,078 Claims priority, application Italy, Apr. 29, 1964, 9,286/64 Claims. (Cl. 103-153) The present invention relates to a pump permitting the metering of small amounts of liquids.

A second aspect of the present invention is a pump which makes possible a good reproducibility for a wide range of rates of flow.

A third aspect of the present invention is a pump permitting the metering of the liquid even against very high pressures.

A further aspect of the present invention is a pump capable of metering low-boiling liquids (e.g., acetaldehyde), viscous liquids (e.g., heavy oils) and which is capable of withstanding both the action of solvents and of corrosive liquids such as nitric acid, nitric solutions of uranium, aluminum chlorohydride, etc.

The micropump of the present invention fulfills the above mentioned requirements since the body of the distribution head has internally a distribution member formed by a metal or Teflon (registered trademark) cylinder which is suitably machined and has in its median portion a throttled section (reduction of the radius of the cylinders cross-section) whose dimensions are such as to allow the input and the output of liquids to be metered when said throttled section is in communication, in its reciprocating movement within the distribution head body, with the input and output ducts which are present in the distribution body.

The pump according to the present invention, besides affording the advantages of a head made in a simple and compact way, is a self-priming pump and thus permits doing away with all expedients for starting its operation. The self-priming effect occurs because of the prearranged phase displacement of the distribution member or valve as regards to the suction piston, which, because of the phase displacement, reciprocates quickly and therefore sucks the liquid, preventing by this the formation of vapor-locks of volatile or low-boiling liquids.

An advantage of the head so manufactured is an uninterrupted metering, i.e., without any possibility of vapor-lock build-up. The particular design of valve eliminates sticking, even though it operates with liquids that tend to polymerize. This feature assures that the flow is reproducible.

In the drawing there is shown a simplified diagram of the head of the pump made according to the invention. Said diagram can obviously be varied according to the individual requirements without departing from the basic principle of the invention.

A reciprocating movement is imparted to the piston 1 (metering) by compressed air coming through port 2 and by the recoil spring 4. The reciprocating movement is effected by compressed air in one direction and by the spring 4 in the other direction. The spring 4 may, however be replaced by compressed air. The length of stroke is adjusted by the adjusting screw 3. The rate of flow of the micropump is a function of the length of stroke of the piston 1 and of the number of reciprocations thereof in the unit time.

ice

The portion 5 (distributing piston), which is located, according to the drawing, perpendicularly to the metering piston 1 but could be set at an angle different from with respect thereto, receives a reciprocating drive by compressed air coming in through port 6 and by a recoil spring 7. The movement of the two members 1 and 5 is attuned in a manner known per se and this attunement can be obtained from a common compressed-air feed having branches to ports 2 and 6 which are fed alternately. The phase displacement is effected by means of a rotating distributor, for instance, which in a revolution of 360 feeds both the pump cylinder and the valve with suitable phase displacement between the two elements 1 and 5. The drawing does not show the feed source, nor the attunement members, either, as they are not a part of the invention. When the piston 1 is at its lower dead-center position, the throttled section 8 (formed by reducing the cross-sectional area of portion 5) is located in registry with input duct 11, thus permitting direct communication to be established between the duct 10 (metering chamber) and the input port 11. By so doing, the piston 1, being lifted towards the upper dead center position (this is preset by the adjusting screw 3), sucks the liquid to be metered until the metering chamber 9 is full. When the piston 1 reaches its upper dead center, the portion 5 is displaced so as to move its own throttled section from input port 11 to the output port 12.

Once the throttled section 8 is in registry with output port 12, the piston 1 starts its down stroke towards the lower dead center, pushing the liquid to be metered out of the metering chamber 9, through the duct 10 and the throttled section 8 to the output port 12.

The cycle is repeated at an adjustable frequency.

In a few actually constructed experimental prototypes a metering reproducibility of $0.01 per rates of flow varying from 0.25 to 800 cu. cms. an hour has been measured. Said reproducibility for the low rates of flow aforementioned can be regarded as excellent.

The reproducibility of the metering is illustrated by the following tables which refer to a compressed-air actuated pump at the pressure of 33.5 kgs./sq. cm. with a piston stroke frequency of 769 strokes per hour and whose minimum and maximum rates of flow are 0.25 cu. cms. per hour and 870 cu. cms. per hour, respectively. (A) With distilled water Rate of flow: 4.32 cu. cms./hour (Samplings at 5-minute intervals, corresponding to 64 strokes each) Consecutive Cu. cms. H O Deviation from the samplings average Average 0. 36

Standard deviation= i001.

Rate of flow: 147.6 cu. ems/hour (Samplings at 7 mins. 48 secs. intervals=l strokes) Consecutive Cu. ems. H O Deviation from the samplings average Average 10.30

Standard deviation $0.02.

Rate of flow: 299.86 cu. cms./hr. (Samplings taken at 3-minute intervals=39 strokes) Standard deviation: 510.03.

(B) With oil (32 Engler at 50 C.) Rate of flow: 19.77 grs./hour (Samplings taken at 6-minute intervals=77 strokes) Consecutive Grs. oil Deviation from the samplings average Average l. 977

Standard deviation $0.048.

Rate of flow: 156.8 grs./hr. (Samplings taken at 3-minute intervals=39 strokes) Consecutive Grs. oil Deviation from the samplings average Average 7. 84

Standard deviation= 10.016.

(C) With acetaldehyde, at a temperature of 24 C.

A buret-te, closed at its upper end with a rubber stopper and mounted vertically with respect to the intake valve is used for feeding-in the liquid; the volume readings are efiected on the intake side and constant values are obtained from consecutive readings of 2 cu. cms. each, with a rate of fiow of 69.23 cu. cms. an hour.

What we claim is:

1. A micropump for repetitive reproducible metering of volatile, very viscous and corrosive liquids comprising a housing, a piston reciprocable rectilinearly in a metering cylinder in said housing, a valve reciproca'ble rectilinearly in fluid-tight relation in a chamber in said housing, said valve being of equal cylindrical diameter adjacent its ends and of reduced diameter intermediate its ends, a supply duct for supplying liquid to said chamber, an output duct for exhausting the liquid from said chamber, a third duct connecting said chamber with one end of said cylinder, means for reciprocating said valve to move it from a first position where its reduced diameter portion registers simultaneously with said supply duct and said third duct and one larger diameter portion thereof shuts off said output duct to a second position in which its reduced diameter portion registers simultaneously with said third duct and said output duct and the other larger diameter portion shuts 011 said supply duct, and means for reciprocating said piston to move it in a direction to suck the liquid into said cylinder from said supply duct through said third duct when said valve is in its first position, and to pump the liquid from said cylinder out through said third and output ducts when said valve is in its second position, the means for reciprocating said piston and said valve including means for supplying compressed air at least to one end of each of said piston and valve to move each in one direction.

2. A micropump as claimed in claim 1, wherein said valve is made of tetrafluoroethylene.

3. A mi-cr-opump as claimed in claim 1, wherein a spring is positioned in both said chamber and said cylinder to resist movement of each under action of the compressed air and to move each in a direction opposite to that in which it is moved by the compressed air when the compressed air pressure is relieved.

4. A micropump as claimed in claim 1, wherein the piston and valve reciprocate in directions at right angles to each other, and the compressed air is supplied alternately to the said ends of said valve andI-piston to move the piston in its liquid-sucking direction when said valve is in its first position and to move the piston in its liquid pumping direction when said valve is in its second position.

5. A micropump as claimed in claim 1, wherein a stop is positioned in said housing to limit the sucking stroke of said piston and is rotatably adjustable to control the length of said stroke and thereby the amount of liquid which can be sucked into said metering cylinder.

References Cited by the Examiner UNITED STATES PATENTS 2,006,879 7/1935 Benedek 10 3227 2,727,466 12/1955 Kling et al. 103-227 2,806,431 9/1957 Woydt 103227 2,857,184 10/1958 Mancuis 103l14 2,935,365 5/1960 Dega 103-114 3,021,890 2/1962 Donini 103-38 DONLEY I. STOCKING, Primary Examiner.

HENRY F. RADUAZO, Examiner, 

1. A MICROPUMP FOR REPETITIVE REPRODUCIBLE METERING OF VOLATILE, VERY VISCOUS AND CORROSIVE LIQUIDS COMPRISING A HOUSING, A PISTON RECIPROCABLE RECTILINEARLY IN A METERING CYLINDER IN SAID HOUSING, A VALVE RECIPROCABLE RECTILINEARLY IN FLUID-TIGHT RELATION IN A CHAMBER IN SAID HOUSING, SAID VALVE BEING OF EQUAL CYLINDRICAL DIAMETER ADJACENT ITS ENDS AND OF REDUCED DIAMETER INTERMEDIATE ITS ENDS, A SUPPLY DUCT FOR SUPPLYING LIQUID TO SAID CHAMBER, AN OUTPUT DUCT FOR EXHAUSTING THE LIQUID FROM SAID CHAMBER, A THIRD DUCT CONNECTING SAID CHAMBER WITH ONE END OF SAID CYLINDER, MEANS FOR RECIPROCATING SAID VALVE TO MOVE IT FROM A FIRST POSITION WHERE ITS REDUCED DIAMETER PORTION REGISTERS SIMULTANEOUSLY WITH SAID SUPPLY DUCT AND SAID THIRD DUCT AND ONE LARGER DIAMETER PORTION THEREOF SHUTS OFF SAID OUTPUT DUCT TO A SECOND POSITION IN WHICH ITS REDUCED DIAMETER PORTION REGISTERS SIMULTANEOUSLY WITH SAID THIRD DUCT AND SAID OUTPUT DUCT AND THE OTHER LARGER DIAMETER PORTION SHUTS OFF SAID SUPPLY DUCT, AND MEANS FOR RECIPROCATING SAID PISTON TO MOVE IT IN A DIRECTION TO SUCH THE LIQUID INTO SAID CYLINDER FROM SAID SUPPLY DUCT THROUGH SAID THIRD DUCT WHEN SAID VALVE IS IN ITS FIRST POSITION, AND TO PUMP THE LIQUID FROM SAID CYLINDER OUT THROUGH SAID THIRD AND OUTPUT DUCTS WHEN SAID VALVE IS IN ITS SECOND POSITION, THE MEANS FOR RECIPROCATING SAID PISTON AND SAID VALVE INCLUDING MEANS FOR SUPPLYING COMPRESSED AIR AT LEAST TO ONE END OF EACH OF SAID PISTON AND VALVE TO MOVE EACH IN ONE DIRECTION. 